1. Field of the Invention
The invention relates to a pixel structure. More particularly, the invention relates to a pixel structure in which a storage capacitor (Cst) has a semiconductor-metal-insulator-ITO (SMII) structure.
2. Description of Related Art
A thin film transistor liquid crystal display (TFT-LCD) is often composed of a thin film transistor (TFT) array, a color filter array substrate, and a liquid crystal layer. The TFT array is constituted by a plurality of TFTs arranged in array and pixel electrodes respectively corresponding to the TFTs. In order to ensure the favorable display data memory and display data retention function of the conventional pixel structure, a storage capacitor is configured in a pixel structure in most cases. For instance, a pixel electrode covers a metal capacitor electrode, so as to form an MII storage capacitor.
According to the related art, a source metal layer is often employed to form the metal capacitor electrode having the MII structure. In some manufacturing processes, e.g., a manufacturing process in which four photo masks are required, a semiconductor layer underlies the source metal layer, and the semiconductor layer and the pixel electrode located above the source can together form a SMII capacitor. The source metal layer exposes a portion of the periphery of the semiconductor layer. The pixel electrode located above the source is connected to the pixel electrode which is not located above the source. Nonetheless, when the semiconductor material is irradiated by light, the semiconductor material is conductive. Thereby, parasitic capacitance is generated by the exposed semiconductor layer and the pixel electrode located above the semiconductor layer according to different operational conditions, e.g., different frequencies, different voltages, and so on. As such, the capacitance of the SMII storage capacitor is changed, and defects (e.g., waterfall, image sticking, etc.) occur on the display frame.